NetLogo User Community Models

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## WHAT IS IT?

(a general understanding of what the model is trying to show or explain)

This model is an agent based model, based on the SI (Susceptible Infectious) model, for HIV transmission among sexworkers in South Africa, and it is meant to assess the effectiveness of PrEP and PEP in this community. The model will show how a group of sexworkers can go from being HIV-, to being HIV+, also taking into account the different dynamics such as the average coupling rate, average condom use among this group, HIV prevalance specific to these people and their prep and pep intake over a period of 25 years. The intention is to monitor how quickly the diseases spreads when there is a certain level of medical intervention.

## HOW IT WORKS

(what rules the agents use to create the overall behavior of the model)

The model works such that one HIV+ individual is introduced to the group. As the simulation takes place the initial group of susceptible ie the sexworkers, is divided into subgroups or classes, where a certain percentage of individuals is HIV +, HIV-, HIV- on PrEP and those on ART, and those in the AIDS class. Those who take PEP will not have a separate class as its part of the HIV- who sought medical intervention upon being exposed and are immediately part of the susceptable afterwards. ALL HIV- are the susceptible, and are recruited into the infected class through sexual interactions with the infected, and whether or not this process is successful depends on the diverse interventions considered by each individual. The model assumes that every individual is susceptable, that is they are sexually active, and are not immune to the infection. The model only assumes the trasmission is through unprotected sex.

The number of ticks measures the time that passes in descrete. The intention is to simulate the real life scenario such that a certain percentage of people are on prep, pep (after exposure) and ART (for the infected), and the desired result is to monitor the effectiveness of prep on the hiv prevelance of the group after a certain time.

Having the information that total adherence to PrEP leads to total immunuty against HIV, this will then be taken into consideration and the individuals on PrEP (which we will consider as complete adherence), will therefore not be infected. Another prevention means is the use of condoms, and therefore the model accommodates varying degrees that different couples will use. Upon the use of condoms, susceptible individuals cannot be infected, and if they arent used they will be infected depeding on the rate of infection.

https://www.unaids.org/en/regionscountries/countries/southafrica

The above source was used for statistics that became part of the variables used in the model, and provides the 2022 data. Other literature has also been used to source data. The estimated population size of sexworkers nationwide is 146 000, have they have an HIV prevalence of 62.3%. Their HIV testing and status awareness is at 81%. The adult aged between 15 and 49 has 17.8% HIV prevalance.

There model also accommodates an exit of individuals from this trade, as well as new administrations of PrEP over time

## HOW TO USE IT

(how to use the model, including a description of each of the items in the Interface tab)

The model has an interface with sliders that enable the user to vary the input values as they wish, which will then impact the results as expeted.

such input value are:

Initial number of sexworkers:
this would be the initial group of sexworker that the program start of with. the slider will allow the user to choose any value between 0 - 3000.

Initial HIV+
this feature is also in a form of a slider.
this is a group that are HIV+ already before the program runs which will be the ones who will definitely not be on PrEP treatment. this is presented as a percentage of the initial group of sexworkers.

Initial PrEP
this slider records an input value for the percentage from the initial sexworkers, which will be administered PrEP. this group of people are considered to completely adhere to the treatment and therefore will not infect their clients or sex partners.

PEP_use_rate:
This allows one to input the the average rate of pep use amongst this community.

ART treatment:
this slider allows the user to set the value of the average rate for use of treatment among the infected.

Condom use and coupling rate
These sliders allow input values used in the simulation. Condom use is recorded as a percentage and the coupling rate is defined as the number of clients a sexworker has per week.

## THINGS TO NOTICE

(suggested things for the user to notice while running the model)

The model also returns numbers of newly infected and people in taking prep, as well as the percentages to the entire group.
There is also a plot of this information for visual reprentation of how these are behaving overtime.

## THINGS TO TRY

(suggested things for the user to try to do (move sliders, switches, etc.) with the model)

The using of sliders to vary input values, as well as looking out for the differet output values.

## EXTENDING THE MODEL

(suggested things to add or change in the Code tab to make the model more complicated, detailed, accurate, etc.)

## NETLOGO FEATURES

(interesting or unusual features of NetLogo that the model uses, particularly in the Code tab; or where workarounds were needed for missing features)

## RELATED MODELS

(models in the NetLogo Models Library and elsewhere which are of related interest)
the HIV sample model in the netlogo library, the 'Spread of diseases' model in the IABM textbook in the netlogo library.

## CREDITS AND REFERENCES

(a reference to the model's URL on the web if it has one, as well as any other necessary credits, citations, and links)